The invention relates to a servo-steering valve for a hydraulic servo-steering arrangement, with an input shaft an output shaft, a torsion rod which acts upon the input shaft and the output shaft relative to each other into a central position, and with a valve which consists of a valve sleeve and a valve shaft which are turned relative to each other upon a rotation of the input shaft relative to the output shaft.
Such a servo-steering valve is generally known. The rotation of the valve sleeve relative to the valve shaft results in a hydraulic flow being provided in one or other direction as a function of the direction of rotation. This hydraulic flow is converted in a hydraulic cylinder into a steering support force. The extent of the steering support force depends here on the steering moment which is applied by the driver via the steering wheel onto the input shaft.
In modern steering systems, it is desirable that the steering process can be influenced from the exterior. In other words, the hitherto single input value of the servo-steering valve, namely the steering moment executed by the driver, is to be superimposed with a superimposition value, which leads to a modification of the steering command. In this way, for example, systems for automatic vehicle stabilization can act on the driving behaviour of the vehicle. Finally, the steering characteristic of the steering system (the steering “feel”), of which the driver is aware via the steering wheel, can be altered.